Is there a BCOP (or substantiated opinion) for negotiating eBGP
Graceful-Restart and Graceful-Restart Helper-Mode with external networks?
Implementation looks varied across a few larger transit providers, and in
some cases implemented inconsistently within the same provider. Seeing
most IX peers with GR disabled, although I don't see they've disabled GR
Helper Mode. Apparently, Junos (12.3, at least) doesn't offer disabling GR
Helper Mode for BGP.
We generally disable GR on eBGP sessions because different
peers (be they customers, upstreams or peers) have different
hardware/software that could make this tricky.
Internally, we run NSR on boxes with dual control planes.
This is recent, as several of your garden-variety (and
exotic) service provider network protocols and services are
now reasonably supported that it makes sense to migrate from
GR to NSR.
We don't generally run GR on boxes with single control
planes, as there could be operational impact when BFD is
involved under some circumstances. That said, GR Helper mode
tends to always be available even when GR is not enabled.